1. Field of the Invention
The present invention relates to a method of recording data on a hard disk drive, and more particularly, to a method of and an apparatus for recording data, by which the recorded data has robustness to an adjacent track erase and an off-track erase, and a storage medium comprising instructions for executing the method.
2. Description of the Related Art
A hard disk drive is a recording apparatus for storing information. Information is generally recorded on concentric tracks in either surface of at least one magnetic disk. The disk is rotatably loaded on a spindle motor, and the information is accessed by a reading/writing head mounted on an actuator arm rotated by a voice coil motor. The voice coil motor receives a current to rotate the actuator, thereby shifting the head. The reading/writing head detects a change of a magnetic field radiated from a surface of the disk to read information recorded on the surface of the disk. In order to record the information on a data track, a current is fed to the head. The electrical current generates a magnetic field to magnetize the surface of the disk.
As a capacity of the hard disk drive increases, a track density becomes greater and an interval between tracks becomes narrower. Therefore, adjacent tracks are affected by a recording magnetic field generated when data is recorded on the track, so that it is more likely that the data recorded on the adjacent tracks is damaged.
The recording density may be increased by shortening a distance between the head and the disk. If the distance between the head and the disk is shortened, the data recorded in the adjacent tracks may be damaged by the recording magnetic field generated by the head.
Such a phenomenon is referred to as adjacent track erase (ATE), and it matters when the recording current applied to the head is too high. Meanwhile, the ATE may be worse by a reduction of coercivity of a medium.
FIG. 1 is a view depicting an effect resulting from ATE. Three tracks are shown in FIG. 1. White portions are indicative of regions recorded with the data in each track. FIG. 1 shows a state of an intermediate track when data is recorded on upper and lower tracks. It is apparent from FIG. 1 that the data recorded in the intermediate track is more damaged than data recorded in the upper and lower tracks. Such results are caused due to ATE, by which data recorded in the intermediate track is erased when data are recorded in the upper and lower tracks.
In order to address the above problem, recent hard disk drives suppress the occurrence of the ATE by measuring an operating temperature of the drive to control a write current or overshoot current according to the measured temperature.
In particular, by using a lower write current and overshoot current at a temperature higher than at room temperature, some of the ATE may be prevented.
In such a method of optimizing the recording current, it is difficult to prevent all of the ATE due to repeated recording of data on a same track.
To provide a time shift function, in recently developed personal video recorders (PVRs), a specific region of a hard disk drive is continuously and repeatedly recorded so that the specific region is more affected by ATE. The time shift function means that an amount of an input broadcast stream corresponding to a predetermined period is buffered during a determined period of time to be provided upon request by a user. To this end, the PVR continuously and repeatedly records the broadcast stream input to the region allocated for the purpose of time shift in the hard disk drive. In this case, since the region is continuously and repeatedly used during the activated period for the time shift function, for example, over 24 hours, the data in the region is likely to be damaged by cumulative effects.
In addition to the ATE, the phenomenon that the data recorded in the adjacent track is erased may happen by off-track erasure (OTE). The OTE is due to a deviation of a recording head from a center of the track during the recording of data.
FIG. 2 is a view depicting an effect resulting from the OTE. Three tracks are shown in FIG. 2, in which white portions are indicative of regions recorded with the data in each track. FIG. 2 shows a state of an intermediate track when the data is recorded in an upper track. It is apparent from FIG. 2 that a portion of data from the data recorded in the middle and upper tracks is shifted to a bottom area relative to that of a lower track. Such results are caused by the OTE occurring in the portion where the data is recorded in the tracks, in which off-track data is in the upper track and a portion of the data is erased in the intermediate track.
Although the OTE is related mainly to a precision of a servo control, it is also related to an external impact applied to the hard disk drive, eccentricity of the disk or the like.
In order to prevent the recorded data from being damaged due to the ATE or OTE, a method of reducing an interval between the tracks in a specific position or recording backup information periodically has been utilized, this method leads to an overhead in data processing.